One of the best guesthouse I've been at in Southeast Asia. May (pronounced Mai) and Lin (Ping-ping and Lucky) were exceptional hosts. They waited for me until 11pm to check in and were so friendly and helpful all the time with everything. The room was on the top floor and it was perfect. Bed was comfortable, AC was good and quiet, the shower was strong and hot, and the room was clean and comfortable. The included breakfast in the morning is a perfect way to start your day. Very simple chicken with rice and vegetable soup, but you can taste it is made with love and care. There is a chocolate, coffee and tea station all day as well.
I found the location to be really nice. Off the main road, under the bridge, along the river and tucked away down a perpendicular street to the river. Ten minute walk to the famous Khaosan street and area, but far enough to be amoung more of the locals than tourists. This side of the river is more relaxed and has lots of nice local shops, cafes, restaurants that you can discover. Take roads where the cars can't go down, or normally shouldn't!
You won't regret staying here. I extended my stay, twice. You get a quality room for a very reasonable price and the a place to rest and relax after a crazy day of exploring Bangkok. Be aware the sky train system does not reach this area, but there are plenty buses that do. There is a convenient bus stop just 5 minute walk from Pailin Guesthouse. Enjoy it!